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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: T on July 30, 2015, 05:11:38 AM

Title: Iron (II) and Potassium permanganate reaction
Post by: T on July 30, 2015, 05:11:38 AM

Hello,

The question is:

Fe²⁺ reacts in a 5:1 molar with a solution containing KMnO4^- and dilute sulfuric acid. What is the reaction equation? Omit spectator ions.

So firstly the spectator ion is K+ so omit that. However, I don't understand what the sulfuric acid is doing? Is it a catalyst or something else? Thank you.

(mod edit to title, sjb)

Title: Re: Iron (II) and Potassium permanganate reaction?
Post by: DrCMS on July 30, 2015, 05:46:37 AM

Hint - acids are a source of what ions?

Also your question title is misleading try to give better descriptions of the question such as "Iron (II) and Potassium permanganate reaction?"


(mod edit to title, sjb)

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: T on July 31, 2015, 02:53:25 AM

Ok, will try to make better titles from now on (could a moderator tell me what the original title was so I can see the difference?); acids are a source of hydronium ions. So it could bond with the permanganate, forming HMnO₄. Thanks DrCMS

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: sjb on July 31, 2015, 03:41:59 AM

Quote from: T on July 31, 2015, 02:53:25 AM

Ok, will try to make better titles from now on (could a moderator tell me what the original title was so I can see the difference?)

I forget exactly, but it was something like "Find the element"

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: Hunter2 on July 31, 2015, 04:35:10 AM

The point is still not found. Hint redox reaction.

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: T on July 31, 2015, 06:01:39 AM

I see.

For the redox reaction:
Fe²⁺  :rarrow: Fe³⁺ + e^-

I am not sure about the reduction of MnO₄^-

MnO₄^- + 5e^- + 8H⁺ :rarrow: 4H₂O + Mn²⁺?

Thanks

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: Hunter2 on July 31, 2015, 06:09:24 AM

Everything is correct.

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: T on July 31, 2015, 06:17:48 AM

I see thanks. However what does the dilute sulfuric acid do?

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: Hunter2 on July 31, 2015, 06:36:38 AM

I think this you should answer yourself now. Look the redox reaction. What happens to the H⁺.

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: T on July 31, 2015, 08:06:30 AM

I see. So if I had NaOH instead of sulfuric acid the permaganate wont react with the iron?

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: Hunter2 on July 31, 2015, 08:21:18 AM

In case of alcaline conditions also it will react. But instead of Mn²⁺ MnO₂ will be formed. In this case water reacts: H₂O + (O) + 2 e^- => 2 OH^-

(O) is the oxygen in the oxidieser here Permanganate

Iron will also precipitate as Fe(OH)₂ which is sensitive to oxygen and easily convert to Fe(OH)₃

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: Borek on July 31, 2015, 08:27:42 AM

In the alkaline solutions permanganate gets reduced to manganate, MnO₂ is produced closer to the pH 7.

This is just a rule of thumb though, sometimes you will get a mixture of products.

Title: Re: Iron (II) and Potassium permanganate reaction
Post by: Hunter2 on July 31, 2015, 08:35:49 AM

This is in my opinion right, if no reducing agent is present. In present of reducing agent (maybe iron-II is not the best on), like Sulfite, Oxalate, etc. Manganaese dioxide will be formed. This will also happen with Manganate -VI and Manganate -V